Water gelation by small organic molecules.

https://nathan.instras.com/documentDB/paper-311.pdf

Poly(ethylene oxide)-poly(propylene oxide )-poly (ethylene oxide) block copolymer surfactants in aqueous solutions and at interfaces: thermodynamics, structure, dynamics, and modeling

Supramolecular nanotube architectures based on amphiphilic molecules.

Dielectric Relaxation and Solvation Dynamics of Water in Complex Chemical and Biological Systems

Almost all biological macromoleculess proteins
(enzymes) and DNAs are inactive in the absence of
water. Hydration of a protein/enzyme is particularly
important for the stability of the structure and for
the function, especially the recognition at a specific
site. This role of hydration in enzyme catalysis is well
known and has recently been reviewed in a number
of publications. In one of these studies it was
shown that the dehydration of a protein, which
makes it more rigid and increases its denaturation
temperature, is correlated with the loss of its physiological function.

Dynamics of water in biological recognition.

Dielectric relaxation and NMR spectrum of water in biological systems such as proteins, DNA, and reverse micelles can often be described by two widely different time constants, one of which is in the picosecond while the other is in the nanosecond regime. Although it is widely believed that the bimodal relaxation arises from water at the hydration shell, a quantitative understanding of this important phenomenon is lacking. In this article we present a theory of dielectric relaxation of biological water. The time dependent relaxation of biological water is described in terms of a dynamic equilibrium between the free and bound water molecules. It is assumed that only the free water molecules undergo orientational motion; the bound water contribution enters only through the rotation of the biomolecule, which is also considered. The dielectric relaxation is then determined by the equilibrium constant between the two species and the rate of conversion from bound to free state and vice versa. However, the diele...

/pdf/dielectric-relaxation-of-biological-water-2zevupbr37.pdf

Dielectric Relaxation of Biological Water

Effect of molecular chirality on the morphology of biomimetic langmuir monolayers.

A detailed theoretical study of solvation dynamics in water is presented. The motivation of the present study comes from the recent experimental observation that the dynamics of solvation of an ion in water is ultrafast and the solvation time correlation function decays with a time constant of about 55 fs. The slower decay in the long time can be described by a sum of two exponentials with time constants equal to 126 and 880 fs. The molecular theory (developed earlier) predicts a time constant equal to 52 fs for the initial Gaussian decay and time constants equal to 134 and 886 fs for the two exponential components at the long time. This nearly perfect agreement is obtained by using the most detailed dynamical information available in the literature. The present study emphasizes the importance of the intermolecular vibrational band originating from the O...O stretching mode of the O–H...O units in the initial dynamics and raises several interesting questions regarding the nature of the decay of this mode. We have also studied the effects of isotope substitution on solvation dynamics. It is predicted that a significant isotope effect may be observed in the long time. The experimental results have also been compared with the prediction of the dynamic mean spherical approximation (DMSA); the agreement is not satisfactory at the long time. It is further found that the molecular theory and the DMSA lead to virtually identical results if the translational modes of the solvent molecules are neglected in the former. DMSA has also been used to investigate the dynamics of solvation of a dipolar solute in water. It is found that the dynamics of dipolar solvation exhibit features rather different from those of ion solvation.

Ultrafast solvation dynamics in water: Isotope effects and comparison with experimental results

Dielectric relaxation of aqueous protein solutions show many anomalous properties. For example, (i) protein solutions have higher static dielectric constant compared to that of pure water, (ii) the real part of the dielectric function (DF) exhibits a crossover with varying concentration, and (iii) the imaginary part of DF exhibits a bimodal frequency dependence. There is no coherent microscopic explanation available for any of these phenomena. Here we present the first unified, microscopic theory of the dielectric relaxation spectra of an aqueous protein solution that explains all the above anomalies, with excellent agreement with all the known experimental results.

Nilashis Nandi

Papers

Dielectric Relaxation and Solvation Dynamics of Water in Complex Chemical and Biological Systems

Dielectric Relaxation of Biological Water

Effect of molecular chirality on the morphology of biomimetic langmuir monolayers.

Ultrafast solvation dynamics in water: Isotope effects and comparison with experimental results

Anomalous dielectric relaxation of aqueous protein solutions